36 

 LXni. The Work of Streams. 



Determine the following" points after a visit to a stream (1) before 

 rain ; (2) after rain : 



1. Where is the stream most rapid ? In shallow or deep places ? 



2. The carrying- power of water of different velocities. 



3. The position of bars and other obstructions in the channel, and 

 the causes. 



4. The cause of variation in width of stream. 



5. When banks are worn away, where are the materials deposited ? 



6. What gives the general direction to the stream ? 



7. Account for the depth of water at bends, and the causes of bends 

 and windings. 



8. When do streams tend to straighten their courses ? 



9. Account for the difference between a gorge and a wide valley. 

 10. Account for the presence or absence of water-falls. 



LXIV. Soils. 



Classifications of Soils : 



1. Loam, composed of equal parts of sand and clay, with some or- 

 ganic matter. 



2. Sandy Loam, in which there is more sand than clay. 



3. Clay Loam, in which there is more clay than sand. 



4. Clay Soil, composed largely of clay. 



5. Sandy Soil, composed largely of sand. 



6. Gravelly Soil, containing many pebbles and small stones. 



7. Humus or Organic Soil, composed largely of decaying organic 

 matter, such as the black soil of swamps, decayed leaves, wood, earth, 

 etc. 



Soils are said to be light when sand is predominant, and as heavy 

 when clay is in excess. The terms Light and Heavy do not refer to the 

 actual weight of the soil, but to the stickiness and the amount of resist- 

 ance it offers to tools of cultivation. 



Properties of Soils : 



1. Physical Properties, the more important being, 



(a) Power to absorb and hold heat. 



(b) Power to absorb and hold moisture. 



(c) Power to absorb and hold gas. 



(d) Power to absorb and hold plant food. 



